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We report the Raman and photoluminescence spectroscopic analysis of layered MoS2 under hydrostatic pressure up to ~ 30 GPa. Unlike previous studies, throughout this work, a special treatment is applied to submerge monolayer, bilayer, multilayer (~ 200 layers), and bulk MoS2 samples directly into silicone oil without a supporting substrate in a diamond anvil cell, thereby eliminating possible interference from substrate–film contact. A thickness-dependent trend is observed for the 2Hc-to-2Ha phase transition: The transition pressure increases from 19.0 to 25.6 GPa as the system thickness is reduced from bulk to multilayer MoS2; a further decrease in thickness to the bilayer structure increases the transition pressure to ~ 36 GPa, as predicted theoretically. This exceeds our measured pressure range, indicating the weakening of interlayer repulsive interactions as the MoS2 film thickness is reduced. Our experiment also reveals a monotonic trend of Raman peak shifting vs. film thickness under applied pressure, suggesting that the Raman vibration modes are more responsive to external pressure in thinner films. The photoluminescence emission peak of the monolayer MoS2 exhibits a blue shift under applied pressure at the rate of 23.8 meV·GPa-1. These results show that the structural and optical properties of MoS2 can be effectively modified by applying hydrostatic pressure.

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Publication history
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Acknowledgements

Publication history

Received: 11 March 2017
Revised: 30 May 2017
Accepted: 01 June 2017
Published: 07 July 2017
Issue date: February 2018

Copyright

© Tsinghua University Press and Springer-Verlag GmbH Germany 2017

Acknowledgements

Acknowledgements

We gratefully acknowledge the financial support of National Natural Science Foundation of China (No. 11404292, No. 31201377, No. 11275203 and 11275205), Fund for Young Backbone Teachers of Universities in Henan Province (Nos. 2014GGJS-085 and 2013GGJS-111), Technological Development Grant of Hefei Science Center of CAS (No. 2014TDG-HSC002), and National Key Scientific Instrument and Equipment Development Project (No. 2011YQ130018).

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